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collected at approximate five-foot intervals and at intervals where staining or color or texture changes are noted. The field staff will examine representative portions of the.soil samples andprepare soil boring logs that describe the encountered soil in general accordance with the American Standards for Testing Materials (ASTM) 2488-06 and the Unified Soil Classification System (USCS). The soil boring logs will indicate the depth of the various strata, and record other pertinent information regarding the advancement and sampling of each borehole. J Each soil sample will be field screened for volatile organic vapors with a photoionization detector(PID)or similar instrument. The field screening readings will be recorded on the soil boring log. A portion of each 1 soil sample will be retained for potential laboratory analysis. The samples will be collected in an acetate ]1 liner and the liners will be out at the desired mas ple interval and sealed with Teflon®tape and plastic caps at each end. All samples will be stored in an ice chest cooled to approximately4 degrees Celsius(°C)with ice. Yv1tJ Vmdor i 1h Upon completion of the soil boring,the monitoring well (proposed well MW-11)will be constructed with no more than 5Jeet-of.0.020 inch slotted Schedule 40 (Sch-40)2-inch diameterpolyvinyl chloride(PVC). The well screen will be located from approximately 20 to 25 feet bgs: Approximately 20 feet of blank Sch 40, —2 2-inch diameter PVC casing will be located from 20 feet bgs to approximately 6-inches below grade. The e north side of the casing will be .otched o facilitate consistent groundwater monitoring data acquisition. Sand pack material consisting 2/20'M`or terey and, or equivalent,will be placed from approximately 25 to 18 feet bgs. Bentonitepellets or cip ii be placed from approximately 18 to 15 feet bgs-Above the h d � bentonite seal the annular space will be filled with Portland type 11 cement(grout)or grout/bentonite slurry to approximately 6-inches.below grade. The surface completion will consist of a traffic rated well box set in concrete with a 2-inch diameter locking well cap. Drill cuttings will be stored on-site in 55-gallon drums pending laboratory results. Soil cuttings will be profiled and disposed of at an appropriate facilitywithing_.0 days. Well installation procedures will be in accordance with the San Joaquin County Well Standards r — At least 72 hours after the installation of the monitoring well, the newly installed monitoring well will be t•, surged with a 2-inch nominal diameter surge block to remove fines from the filter pack. Subsequent to surging, the well will be developed using cent irfugal pump until the produced water is relatively sediment free(10 NTUs)or until a volume equivalent to at least 10 well casings of water have been removed,which I ever occurs first. All purge water will be stored in 55-gallon drums and staged on-site pending laboratory j analysis for disposal. The development of the well will be performed a minimum of 72 hours after u installation. f' At least-72 hours after completion of the monitoring well surging and development, ATC will return to the �l Site to collect-groundwater samples. Prior to collection of groundwater samples,dedicated_polyethylene sample tubing will be inserted to the depth equivalent to midway down the screened interval so as not to �I disturb the standing wafer column above the screened interval and not to stir 1]p colloidal particles or .`' sediment. The tubing will then be connected to a peristaltic_pump and a Horiba Water Quality Monitor Model U-22XD meter (or equivalent) with a flow-througl cell LGroundwaterwill be slowly-pumped while simultane sl monitoring the DTW and adjusting the-pumprate until no or minimal drawdown obse.rv_ed. Drawdown greater than 0.33 ft results in a reduction of pumping rate or a temporary_shut down. Once the pumping rate is stabilized at a rate not exceeding 0.5 L/min, temperature, pH, specific conductance, dissolved oxygen, and turbidity will be measured-When` three consecutive readings show the parameters are stabilized, a groundwater sample is collected from the tubing port in front of the flow through cell of the meter. I -- Water samples will be collected from the tubing and carefully poured into 40-milliliter (ml) glass vials preserved with hydrochloric acid. The vials will be filled to produce a positive meniscus and sealed with a =s V �� Additional Investigation Workplan 2'o Addendum CA NA �� ,• Quik Stop No. 132,Stockton,CA November 03,2009 { s